$('.mj_item').click(function(){
	
	var offset_this = $(this).offset();
	var offset_selected = $('.selected').first().offset();
	
	if(offset_selected && offset_selected.left == offset_this.left){
		
		if(offset_selected.top < offset_this.top){
			$('.mj_item').each(function(){
				var offset_tmp = $(this).offset();
				if(offset_tmp.left == offset_this.left && offset_tmp < offset_this.top){
//					$(this).animate({top:'+='+(offset_this.top-offset_selected.top)+'px'}, 2000);	
					alert(offset_this.top-offset_selected.top);
				}
			});
		}
		
	}
	
	$('.mj_item').removeClass('selected');
	$(this).addClass('selected');
	
});